• 대한공업교육학회지
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• 제34권1호
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• pp.274-286
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• 2009

광섬유 센서는 음향이나 진동을 계측하는 곳에 광범위하게 사용된다. 특히 간섭계형 광섬유 센서는 이러한 물리량을 계측하는데 더욱 적합하다.본 연구에서는 페브리-페롯 간섭계형 광섬유 센서를 이용하여 파이프 내에서 발생하는 유체유기진동을 측정하였다. 이러한 진동은 또한 가속도계로도 측정하였고, 두 측정치를 서로 비교하였다. 파이프에서 벤츄리, 노즐, 침출 배럴, 급 확대관 등에 흐르는 유체로 인한 진동을 계측하였다. 유량은 50 L/min에서 150 L/min로 변화시켰고 파이프 내를 흐르는 유체의 평균 유속은 7 m/s정도였다. 실험결과에 근거하여 제안된 광섬유 센서는 유체유기진동을 잘 측정하였고 따라서 이러한 시스템은 파이프라인이나 케이블, 빌딩등에서 발생하는 유체유기진동으로 인한 시스템 모니터링에 적용할 수 있을 것으로 판단된다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 1994년도 추계학술대회논문집; 한국종합전시장, 18 Nov. 1994
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• pp.265-270
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• 1994

본 연구에서는 케비테이션 터널에서의 경사진 원형실린더의 유동유기진동시험을 통하여 경사각에 따른 유동유기진동 특성규명과 아울러 유체력 계수들의 실험적 산정을 시도하였으며 도출된 주요한 결론은 다음과 같다. 경사각이 20.deg. 이상되면 마찰저항력에 비해 수직항력이 지배적이 되며, 이때 수직항력계수는 여러 관찰자에 의해 관측된 범위의 값(1.7-2.0)을 갖는다. 또한, 양력계수 $C_{L,rms}$은 유속범위 4$_{n}$D<8의 범위에서 lock-in 현상에 의해 큰 값을 갖게 되며, 경사각이 커질수록 큰 값을 갖는다. 경사각이 30.deg.인 경우 최대값은 약 0.9, 20.deg.인 경우 0.4로 계측되었다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.921-926
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• 2002

In this study, we investigate the plugging effect on the CE type steam generator tube. The natural frequency and mode shape will be changed due to decrease of the effective mass distribution along the tube. We compared the variation of stability ratio for plugged tube with that for unplugged one. The natural frequency increased because of removing the cooling water inside the steam generator tube, but the stability ratio decreased inversely because of changing the vibrational model shape. We also investigated the turbulent excitation effect.

• 대한조선학회논문집
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• 제28권2호
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• pp.95-103
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• 1991

유체흐름중에 있는 원통형부재의 질량비에 따른 와유기진동특성을 파악하기 위하여 일련의 시험이 수행되었다. 실험은 질량비가 서로 다른 5개의 시험봉(길이 60cm:직경 6mm)을 제작하여 해사기술연구소의 공동수조에서 실시하였다. 주요 실험결과로서 원통형부재에 고진동을 유발하는 유체속도의 범위는 질량비에 따라 변화하며, 가벼운 원통형부재가 무거운 원통형부재에 비하여 더 넓은 유체속도 범위에 걸쳐 고진동현상을 나타냄이 정량적으로 밝혀졌다.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2001년도 추계학술대회논문집 II
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• pp.1400-1405
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• 2001

In this study, an analysis program to assess the susceptibility of steam generator tubes due to the flow-induced vibration was developed. Analysis of fluid-elastic instability and random turbulence excitation for the U-tube bundle in CE-type steam generator was accomplished. The effective mass distribution along the U-tube was obtained to calculate the natural frequency and dynamic mode shape. Finally, stability ratios and rms vibration amplitude for selected tubes are obtained.

• 한국전산유체공학회지
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• 제16권1호
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• pp.73-82
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• 2011

In this paper, the vortex-induced vibration of circular cylinders is studied using the immersed boundary method on the Cartesian mesh. The Reynolds numbers considered is from 100 to 200. Using the configuration of tendemly arranged multiple circular cylinders, the vortex shedding behind of the cylinders and their flow-induced motion are investigated. The staggered MAC grid arrangement, which is the typical grid system for the incompressible flow on the Cartesian meshes, is utilized. Pressure correction method is applied for solving the divergence-free incompressible velocity field. The body motion is described by immersed boundary technique that has advantages for moving object on the fixed computational domain. It is also discussed for the computational noise in hydrodynamic forces when body motion is represented by the immersed boundary method. The Predictor/Corrector method is used for simulating the nonlinear response of the elastically mounted cylinder excited by vortex-shedding.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2003년도 추계학술대회논문집
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• pp.446-451
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• 2003

This paper presents some examples of active control of flow-induced vibration using piezoelectric actuators. The flutter phenomenon, which is the dynamic instability of structure due to mutual interaction among inertia, stiffness, and aerodynamic forces, may cause catastrophic structural failure, and therefore the active flutter suppression is one of the main objectives of the aeroelastic control. Active flutter control has been numerically and experimentally studied for swept-back lifting surfaces using piezoelectric actuation. A finite element method, a panel aerodynamic method, and the minimum state space realization are involved in the development of the governing equation, which is efficiently used for the analysis of the system and design of control laws with modern control framework. The active control suppressed flow-induced vibrations and extended the flutter speed around by 10%. Another representative flow-induced vibration phenomenon is the oscillation of blunt bodies due to the vortex shedding. In general, it is quite difficult to set up the numerical model because of the strong non-linearity of the vortex shedding structure. Therefore, we applied adaptive positive position feedback controller, which requires no pre-determined model of the plant, and successfully suppressed the flow-induced vibration.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2002년도 추계학술대회논문집
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• pp.927-932
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• 2002

The stability ratio and vibrational amplitude of each tube inside a steam generator have different values. We estimate the characteristics of flow-induced vibration for CE type steam generator with various column and row number of the tube. To obtain the thermal-hydraulic data and stability ratio we use the ATHOS3-MODI and PIAT-FEI/TE code respectively. It turns out that the steam generator has a bounded central zone with the distributed values of the stability ratio and the vibrational amplitude, and those values across the zone boundary become decreased.

• 한국소음진동공학회:학술대회논문집
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• 한국소음진동공학회 2011년도 춘계학술대회 논문집
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• pp.693-699
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• 2011

The outermost SG tubes have more structural problems than inside tubes. Many studies have used a uniform added mass coefficient for all of the SG tubes during the FIV analysis. The purpose of this study is to find out the added mass coefficients for each tube in a cylindrical shell. When a number of tubes are increased, added mass coefficients are also increased. And added mass coefficients at outermost tubes are less than those of inside tubes. According to gap changes between outermost tube and cylindrical shell, added mass coefficients are decreased with increasing the gap. When the gap has very large value, it shows that the added mass coefficient is asymptotically converged to the value of the tube array in a free fluid field.

• 한국소음진동공학회논문집
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• 제26권2호
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• pp.203-209
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• 2016

According to the wear detection history for the steam generator tubes in the nuclear power plant, the outer tubes inside the steam generator have more problems on the flow-induced vibration than inner tubes. Many researchers and engineers have used a specified added mass coefficient for a given tube array during the design stage of the steam generator even though the coefficient is not constant for entire tube in cylindrical shell. The aim of this study is to find out the distribution of added mass coefficients for each tube along the radial location. When numbers of tubes inside a cylindrical shell are increased, values of added mass coefficients are also increased. Added mass coefficients at outer tubes are less than those of inner tubes and they are decreased with increasing the gap between the outermost tube and the cylindrical shell. It also turns out when the gap between the outermost tube and the cylindrical shell approaches infinite value, the added mass coefficient converges to an asymptotic value of given tube array in a free fluid field.